A survey of the northern sky

Sky Watch: This week, Ian Griffin woud like you to join him on a whistle-stop tour of the northern sky.

Ian Griffin

With first-quarter moon occurring next Monday, moonlight won't really be a distraction as we explore some of the most storied constellations in the heavens.

You won't need a telescope or binoculars to take part in our panoramic survey, but a comfortable deck-chair and an observing spot with an unobstructed view to the north will increase your comfort and enjoyment no end.

We begin our journey with the constellation Orion. By 8pm, the Hunter is starting to get fairly low in the northwest, but even from the centre of a town or city, the three stars which comprise its distinctive belt and the bright stars Betelgeuse and Rigel should be easy to locate.

It's worth noting the colour of Orion's brighter stars, since their colour tells us their surface temperatures. Blue stars like Rigel, whose surface temperature is over 12,000degC, are much hotter than red stars such as Betelgeuse (whose surface temperature is just 3500degC).

Once you have feasted upon Orion's celestial delights, cast your gaze eastwards, pausing for a moment to take in the bright white star Procyon, in the constellation Canis Minor.

According to legend, Canis Minor was one of the two faithful dogs which followed their master Orion across the sky.

Astronomers have measured the distance to Procyon as just over 11 light years, which means that it is one of the closest bright stars to Earth.

If you have an unobstructed view of the northern horizon, and look below Procyon, you should be able to spot another couple of distinctively coloured stars, the orange hue of Pollux and blue-white Castor, the two brightest stars in Gemini.

To the east of Gemini is Cancer, another constellation of the Zodiac. To be honest, Cancer is a region of the sky devoid of any interesting bright stars, so we will move on swiftly to explore Leo, the Lion, the inverted head of which resembles a fish hook suspended beneath the bright blue star Regulus.